The present invention relates generally to methods of patterning by preferential deposition of material according to an interference pattern directed onto a substrate, and to articles made by the method.
Many techniques have been developed for patterning deposited material on a substrate. A large number of these techniques involve the use of masks to create the desired pattern. For example, material can be deposited over a mask on a substrate. The mask can then be removed, leaving material on those portions of the substrate that were left exposed by the mask. Other techniques involve forming a uniform coating of material, placing a mask over the coating, etching the portions of the coating exposed by the mask, and removing the mask. In many cases, and especially in situations where the pattern dimensions are small, the mask is made by photolithographic techniques. Photolithography typically entails coating a photoresist layer, selectively exposing the photoresist to light, developing the photoresist, and removing the developed (or undeveloped) portions of the photoresist. These steps create the mask. Including the mask-making steps, mask-based patterning techniques typically require many processing steps, each of which can be time consuming.
The present invention provides methods of patterning materials on a substrate, for example to form wire grid type reflectors and/or polarizers or other optical elements. The present invention involves selectively heating a substrate according to the maxima and minima of an interference pattern directed onto the substrate. Material can be preferentially deposited on the substrate based on the temperature differences created by the interference pattern. Methods of the present invention can be used to selectively deposit materials without the use of a mask. Methods of the present invention can also be used to pattern substrates in just a few, or even in one, steps. Methods of the present invention can also be used to deposit superimposed patterned structures on the same substrate by either serially or simultaneously depositing material according to different interference patterns.
In one aspect, the present invention provides a method for preferentially depositing material on a substrate surface to make a wire grid optical element, which includes the steps of directing an electromagnetic interference pattern onto the substrate surface to preferentially heat selected portions of the substrate surface according to the interference pattern, and selectively depositing conductive material on the substrate surface according to the interference pattern by exposing the substrate to the conductive material in the gas phase, the material capable of preferentially accumulating as a function of surface temperature.
In some embodiments, mutually coherent beams can be overlapped on the substrate surface to form the interference pattern, and material can be deposited to form structures having dimensions roughly determined by the dimensions of the interference pattern. In these embodiments, structures that have dimensions and/or spacings that are smaller than the spot size of the overlapped beams can be deposited on the substrate without using a mask.